This invention relates to a numerically controlled machine comprising a microprogrammable computer.
In general, a numerical controller or a numerical control device for a numerically controlled machine has to carry out a number of operations and functions in order to control the machine. Such functions comprise interpolation, control of servo systems of the known follow-up type, readout of command data, preparatory processing for the interpolation of the read-out data, display of inside data, and sequence control of an operation panel and/or a power board. Among others, the interpolation and the servo system control are essential or basic functions of a numerical control device and have to be carried out to successively produce the results at a high rate of the order of a microsecond. In contrast, the other functions may be executed to bring about the successive results at a relatively low rate of the order of a millisecond. The recent trend is to require a higher rate of carrying out the basic functions into effect.
Heretofore, a numerical control device of a conventional numerically controlled machine has comprised random logics designed in compliance with the respective functions. On the other hand, it has recently turned out to be feasible due to a reduction in the cost to use a small-sized electronic digital computer, such as a minicomputer or a microcomputer, as a numerical control device. In fact, various computerized numerical control devices are in practical use. It is, however, to be pointed out that the computer sequentially deals with various data in compliance with a program and that the rate at which the results of the basic functions are obtained is insufficient even with a small-sized computer of the highest available speed in contrast to a numerical control device comprising random logics whereby it is possible to deal with various data in parallel. As a result, it has been inevitable either to be satisfied with coarse interpolation with the basic functions deteriorated or to resort with the cost raised to an additional hardware circuit, such as a linear interpolator, for carrying out the basic functions at a high rate.
In the meantime, a microprogrammable or microprogrammed computer has been developed which comprises a memory in a control section, usually called a control memory or storage in contrast to a main memory and an external memory. Programs, called microprograms, are stored in the control memory to supply control signals to the main memory, an arithmetic unit, and/or I/0 devices. Usual programs stored in the main and/or external memory are named macroprograms. A microprogrammable computer has an excellent flexibility of operation because it is possible to optionally vary architecture of the computer by a mere change in the microprograms. A microprogram comprises a sequence of microinstructions having a greater number of bits to directly control operation of the computer than macroinstructions of a macroprogram. Although the individual microinstructions are executed at a high speed of the order of several hundreds of nanoseconds, a number of microinstructions are necessary in order to execute the macroprogram in usual. A microprogrammable computer therefore has a lower speed of operation than a general computer.